The usual suspects - you can do true cross-system comparisons neither here nor elsewhere where cameras are used for obtaining data.

-Both use the same bayer pattern. Can't explain the weird results in any way.
-Microlenses do no make the lens peak at f4 on one camera and at f8 (well into diffraction territory for the resolution) on the other camera, nor will they make f4 and f5.6 worse on the other camera.
-The sensors have pretty similar resolution, CA can't explain the weird differences.
-Canon does not manipulate RAW. Nikon is not really known for that either, and manipulation RAW to have the results be sub-par at f4 and f5.6 but better than possible at f8 makes little sense.
-Must be a very bad RAW converter if it produces such odd results on its own.

It is nonsense that you can't compare them, what you can't do is compare actual numbers but you of course can compare the trend. Here especially, and elsewhere.

The usual suspects - you can do true cross-system comparisons neither here nor elsewhere where cameras are used for obtaining data.

I put + in reputation of this message because
- It is clear statement that you have mentioned many many times
- over simplifying and comparing of raw numbers without understanding the meaning makes nonsense.
The tests here represents the Einstein dilemma - Everything should be made as simple as possible, but not simpler
@Birghtcolor - You make many assumptions. You dont look at the whole itemlist but only separately - one by one.,